A disabled woman has won a High Court challenge over how much she should contribute to her local council care services.

Lawyers for 35-year-old "KM", who cannot be identified for legal reasons, said her legal victory should clarify the law and end the problem of inconsistent policies across the country on the level of contributions vulnerable people have to make to their care.

K, who has severe learning disabilities and lives at home with her parents, won a ruling that Northamptonshire County Council was "exaggerating" contributions after failing properly to apply Government guidance.

Mr Justice Gilbart, sitting in London, said the council's current method of calculating charges under its "fairer contributions policy" was legally flawed and "adds about one third to the current level of contribution".

The judge said the difference might be "a slender one" on one way of looking at K's case, but the policy "may affect large numbers of others whose contributions are also being exaggerated through NCC's failure to apply the national guidance or to make its policy sufficiently clear".

The judge said he had come to his decision after "excavating the statutory basis" of payments "from the almost impenetrable morass that makes up relevant welfare benefits law".

Government guidance had set out a broad framework to help councils ensure their charging policies were fair and consistent.

Anne-Marie Irwin, the specialist lawyer at Irwin Mitchell who represented KM, said: "This case considered whether Northamptonshire County Council's policy was in line with nationwide guidance, in terms of the amount our client has to pay towards the cost of her care.

"This is an important decision which showed that she was being charged more by her local authority than the law allows.

"The ruling means she retains more of her own already limited income in order to get the best from life and meet the needs she has as a result of her disability.

"It is believed Government guidance in relation to this issue has been open to varying interpretations, meaning the policies of local authorities across England and Wales could differ significantly.

"This judgment spells an end to such inconsistencies and could have a major bearing on the amount that vulnerable members of society are asked to pay towards their essential care needs."